Surgical procedures for replacement of a deteriorated or injured hip joint have employed a number of prosthetic devices which have endeavored to address the problems of ease of use, durability of the prosthesis, adjustment thereof, precision in positioning of the prosthesis as well as preservation of as much of the original bone structure as is practical in light of the extent of the development of arthrosis or of an injury that may have occurred.
In one type of arrangement such as that disclosed in U.S. Pat. No. 4,115,875 a tapered and curved shaft is provided for intramedullary positioning in the femur. While this and similar structures have enjoyed widespread use, they suffer from a number of significant disadvantages. Among these, prominent is the difficulty in anchoring the shaft in place. Under conventional procedures, the shaft has typically been forcibly inserted by the practitioner often with the aid of a mallet or similar tool. The type as well as frequency of damage to the femur has greatly contributed to the failure of this type of prosthesis and complication of the surgical procedure. In addition, the durability of the shaft member, once inserted has not been satisfactory due to the tendency of the shaft to become loose and to move relative to the femoral cavity. In addition, removal of the prosthesis for readjustment or replacement is time consuming and difficult for the patient.
Other devices have attempted to solve the anchoring problem but, in general, these solutions have been at the expense of the integrity of the prosthetic implant, have been difficult to set in place or have imposed concentrated stresses along the length of the femoral cavity thereby resulting in potential damage to the femur. In this connection, reference may be had to U.S. Pat. Nos. 3,846,846, 4,520,511 and 4,530,115.